For example, JP 2007-71596 A, which corresponds to US 2007/0051599 A1, discloses a collision detecting apparatus for a vehicle. The collision detecting apparatus includes a pressure sensor disposed in the inside of a vehicle side door to detect a change in pressure inside of the side door caused by deformation of the side door in the event of a collision. The collision detecting apparatus detects a side collision of the vehicle based on the change in pressure detected by the pressure sensor. When the collision is detected, side airbags and the like are activated to protect an occupant from an impact of the collision.
In the event of the collision to the side door, the increase in pressure inside of the side door due to the deformation and vibrations of a side door member due to the impact of the collision and the travelling of the vehicle are likely to occur simultaneously. Therefore, a pressure sensor used for such a collision detecting apparatus is applied with the increase in pressure and the vibrations in a superimposed manner. As such, a detection value of the pressure sensor contains the influences by the increase in pressure and the vibrations, and thus it is difficult to accurately detect only the change in pressure inside of the side door.
The collision detecting apparatus of JP 2007-71596 A has the pressure sensor and a vibration sensor. The pressure sensor has a diaphragm disposed to face a closed space provided inside of the side door. The vibration sensor has a diaphragm isolated from the closed space. A detection value of the vibration sensor is subtracted from the detection value of the pressure sensor so as to remove the influence by the vibration of the side door from the detection value of the pressure sensor.